The present invention relates in general to continuous glass fiber manufacture and, more particularly, to an improved method and apparatus for drying sized fibers.
Glass fiber packages are commonly manufactured by supplying molten glass to a bushing, drawing glass fibers from the bushing, and applying a size to the fibers by an applicator roller. The sized fibers are gathered into a strand at a gathering shoe and are wound on a collet to produce a glass fiber package. The glass fiber package is then transferred via a carrier device to a heated enclosure, such as an oven, where water is evaporated from the aqueous based size.
However, a migration problem generally exists in the resulting glass fiber packages due to the off-line drying process. Migration occurs during the drying process as water in the aqueous based size travels toward the outer surface of the package. As the water moves outwardly, it takes with it a portion of the soluble solids which becomes deposited at the outer periphery of the package, thus resulting in strands which do not have a uniform mount of sizing solids along their length.
The problem of migration has previously been dealt with by simply removing the high solids fibers from the package. However, this solution results in a substantial amount of scrap and, hence, is not cost-effective.
Other attempts have been made to dry the fibers during an in-line process to improve the uniformity of the handling and subsequent processing of size coated strands. For example, Roscher, U.S. Pat. No. 3,619,252, and Smith, U.S. Pat. No. 3,717,448, teach the use of high frequency dielectric heaters or microwave units to dry wet glass strands before they are subsequently packaged or processed.
Unfortunately, a disadvantage of such dielectric heating methods is that they utilize a varying electrostatic field which results in nonuniform heating and hence drying of the coated fibers.
Accordingly, there is a need for an improved in-line process for drying sized fibers which results in the reduction or substantial elimination of migration, and which provides efficient, uniform heating and drying of the sized fibers.